CHAPTER 7
SQL Tuning Techniques

Whenever the query optimizer is unable to automatically generate an efficient execution plan, some manual tuning is required. For that purpose, Oracle provides several techniques. Table 7-1 summarizes them. The goal of this chapter is not only to describe these techniques in detail but also to explain what each technique can do for you and in which situations you can take advantage of them. To choose one of them, it is essential to ask yourself three basic questions:

• Is the SQL statement known and static?
• Should the measures to be taken have an impact on a single SQL statement or on all SQL statements executed by a single session (or even from the whole system)?
• It is possible to change the SQL statement?